The present invention relates to a connector according to the preamble of claim 1 for connecting a three-phase cable.
The invention also concerns a manufacturing method for the connector.
Connection of a three-phase squirrel-cage or synchronous motor in inverter-driven systems is most frequently performed by means of a copper or aluminium cable having three symmetrically placed phase conductors surrounded by a common concentric earth conductor. Connection to the drive acting as the load is conventionally performed using a terminal block at low current levels and cable lugs at higher current levels. The concentric earth conductor is bundled into a "tail" diverted from the side of the cable and then connected using either of the above-mentioned termination methods.
Such a termination method has several shortcomings. Firstly, the joint unavoidably becomes long end bulky, because the phase conductors must be diverted apart from each other prior to the jointing. Secondly, at least four separate jointing steps must be carried out, three for the phase conductors and one for the earth conductor. In the case of segmental phase conductors, they must be dressed into a round shape before jointing. Besides the connections, the cable must be secured by means of a separate strain relief.
The phase and earth conductors, which are diverted apart from each other for the connection, form loops and radiating dipoles for the currents passing through them thus giving rise to stray inductances and emission of electromagnetic fields to their surroundings. To avoid such interference, the phase conductors should be arranged to run as symmetrically and as close to each other as possible. Furthermore, the length of the phase conductors exposed from under the concentric earth conductor should be minimized.